How to set up Time Machine backups to an external USB drive

October 21, 2011 in Mac OS X

There are two types of people in the world: Those who have forever lost important computer files, and those who haven’t…YET! Most people in the first group have learned their lesson (the hard way) and are now backing up their computer on a regular basis. If you are in the second group you have two options:

  1. Experience a painful loss of important photos, videos, music, emails and documents, and THEN start backing up, or
  2. Learn from the first group and start backing up your computer NOW!

It’s your choice, but don’t say you haven’t been warned. All hard drives will fail, it’s just a question of when. Even computer geeks accidentally delete a folder of important files when they meant to delete something else. If you back up your computer regularly and correctly, these otherwise devastating catastrophes become a minor hurdle that you can overcome quickly. And you’ll pat yourself on the back for being so intelligent for having a good computer backup.

External hard drives are a great way to back up your computer and they are now amazingly cheap. In this video I show you how easy it is to plug one into your computer and quickly set up the Time Machine application that comes with your Mac. You’ll be breathing easier in no time at all.

Video too small? Watch full screen by clicking the YouTube Full Screen button button here

What Time Machine does

There are many backup applications out there and many perform most of the functions of Apple’s Time Machine. Your external drive may have even come with backup software. I wouldn’t bother with it. What Time Machine has going for it is it:

  • Keeps previous versions of files that have changed;
  • Lets you browse and recover old files from the Finder and also directly from other Apple applications like iPhoto, Address Book, Mail;
  • Is FREE!

Time Machine doesn’t make a full backup of your computer every time it runs. It only does a full backup the first time. After that, it’s intelligent and only copies the files that have changed (this is called an “incremental backup”). As you’ll see in its preferences window, Time Machine keeps:

  • Hourly backups for the past 24 hours
  • Daily backups for the past month
  • Weekly backups for all previous months

The only constraints on how far back these backups go are the capacity of your backup drive and how big each incremental backup is. If you mainly use your computer for surfing the web, each hourly backup will likely be small (and quick) and your Time Machine backups will ultimately go far back in time. But if you download, create, or edit lots of big video files and your backup drive isn’t a lot bigger than your internal drive, your Time Machine backups won’t go back as far. In that case, you’ll still have a backup copy of every file, you just won’t have as many historical versions of them.

Setting up Time Machine

Before setting up Time Machine, you first need to plug your external drive into your computer. It’s perfectly fine to plug in an external drive while your computer is on. (But do NOT unplug it without reading the important instructions later in this article.)

New external drives often show up on your Desktop with the brand name and model (for instance, in the above video, mine is “WD Passport”). The first thing I like to do is change that name to something that describes what I’m using the drive for. This is especially useful if you ever have more than one of these drives. It will make it immediately obvious which is your Time Machine Backup and which is your iTunes Music Library. You can change the drive’s name by clicking on the name under the drive’s icon and holding for two seconds. When you let go of your click, the drive’s name should be highlighted and editable. Just type the new name and hit Enter.

You can start configuring Time Machine by clicking on its icon if it’s on your Dock, or launching System Preferences and clicking on the Time Machine icon there. You tell Time Machine which drive to use for backups by clicking the “Select Backup Disk…” button, selecting your newly plugged in drive, then clicking the “Use for Backup” button. Time Machine will schedule your first backup to start in just two minutes. If you want Time Machine to back up your whole internal drive (and in almost all cases this is what you should want), then you can just sit back and wait for Time Machine to do its thing.

If you need to exclude some items from your Time Machine backup, you can do that by first clicking on the “Options…” button, then clicking the “+” button, and choosing which folders or files you want to exclude. Normally you’d want to backup everything just in case. Some reasons to exclude items from your backup are:

  • Your external backup drive is not big enough to back up your whole internal drive;
  • You have folder(s) of temporary files you know you will never need and that change frequently (meaning they’ll slow down each backup process with updated files you’re never going to want)
  • You already have backups for a specific folder and want to leave more space in Time Machine for more historical copies of your other stuff.

Time Machine on the menu bar

Before closing the Time Machine preferences window, I like to check the “Show Time Machine status in the menu bar” box. That will put a little Time Machine icon Time Machine menu bar icon on the right side of your menu bar. This is a handy place to:

  • Check Time Machine’s status (either the time of its last backup, or its progress on a currently running backup);
  • Manually start a backup before the next scheduled time using the “Back Up Now” option;
  • Stop a backup in progress using the “Stop Backing Up” option (not recommended, but sometimes you just have to eject your drive and pick up your laptop);
  • Access to the Time Machine Preferences window;
  • “Enter Time Machine” to actually see what files were on your computer in the past and recover them if necessary.

Even though Time Machine will perform a backup every hour, I still sometimes use the “Back Up Now” option. It’s really handy if I’ve just completed some brilliant work and need to grab my laptop and go somewhere. It gives me peace of mind knowing that I’m not carrying the only copy of my work in my MacBook Pro that can be stolen, dropped, or have coffee spilled on it.

Time Machine problems

Time Machine usually runs nearly silently and invisibly with no problems. Just make sure you don’t unplug your external drive without ejecting it, and try to not shut down or put your computer to sleep during a backup process (although it will usually recover even from that). The most likely problem you may see is the “Time Machine could not complete the backup” popup window with the dreaded message that starts “This backup is too large for the backup disk.”Time Machine could not complete the backup

Time Machine offers two suggestions to solve this problem:

  • Select a larger backup disk or
  • Mark the backup smaller by excluding files.

As you saw in the video above, having a backup drive just a little bit larger than the stuff you want to back up does not work. As you can see in the error message, “Time Machine needs work space on the backup disk, in addition to the space required to store backups.” This is why you can’t assume that Time Machine will back up fine just because the space available on your external drive is larger than the “Estimated size of full backup” that you’ll see in the Time Machine Options window. Time Machine doesn’t give you any insight into how much “work space” it needs but I’ve seen estimates that 20-25% extra space is required.

If you really have to use an external drive that’s just big enough to fit everything you need to back up, you can use the method I was forced to use in the video. Find one or more large folders (photos, iTunes, etc.) and use the method described above to exclude them from your backup. Remember, you are just doing this temporarily. Let Time Machine perform its first backup successfully, then go remove the items you added to the exclusion list, and then have Time Machine perform another backup. This works because the second backup will not need as much “work space” as backing up everything in the first backup. NOTE: You will have a backup of each file, but you will likely never have much history of previous versions of files. So you won’t really be getting the full benefit of using Time Machine.

How big a disk?

To get the full benefit of having many hourly, daily, and weekly historical copies of your files, I suggest getting an external drive that’s two to three times larger than your internal drive. If you could afford to buy your Mac, then you have no excuse to not buy a backup drive for it. They are dirt cheap!

There are thousands of models to choose from. You don’t absolutely have to buy one that says it’s for a Mac, but if you don’t you may have to reformat the drive before setting it up with Time Machine. If you know how to do that, great. If not, don’t worry, there are lots of drives that come already formatted for the Mac and they’ll usually brag about it in their product name or right on the box.

Prices vary but, in general, you will pay more for greater capacity and a smaller case. For instance, as of right now (October 21, 2011) on you can get a good 1 TB drive (Western Digital My Book for Mac 1 TB USB 2.0 Desktop External Hard Drive) for $86.89. Surprisingly, the 2 TB version of the same model (Western Digital My Book for Mac 2 TB USB 2.0 Desktop External Hard Drive) is only a bit more, $97.95. Yep, for about the cost of a couple grande vanilla lattes you can get double the capacity.

Or, if you find those two and half pound models too clunky, you can get a smaller package but you’ll pay about the same for less capacity. This 750 GB external drive (Western Digital My Passport for Mac 750 GB USB 2.0 External Hard Drive) is $93.81 (as of Oct 21, 2011), could easily fit in your pocket, and weighs less than seven ounces! But remember, 750 GB is only 3/4ths of 1 TB.

All these prices are sure to change in the near future so here are the current prices, live from

If history is any indication, these prices will almost certainly go down and/or drive capacities will increase. Please, do not let either of these make you delay getting an external drive if you currently have no backups!

Ejecting the right way

If you have a desktop Mac, there’s no reason to ever unplug your external drive. Just let Time Machine back up your computer whenever its on.

If you have a Mac laptop, you’ll probably want to unplug your external drive whenever you move the computer. Do not unplug your external drive unless you use the EJECT command first. You find it in the Finder’s File menu or simply right-click (or Control-click) on the external drive’s icon and choose the Eject command from the contextual menu that pops up. Whichever you do, WAIT until the icon disappears. Only then can you safely unplug the drive. Failure to follow this method could cause you to lose valuable files.

So, if you aren’t currently backing up your Mac, please do so soon. Someday you’ll be very happy you did.

[Disclaimer: If you purchase using any of the links or buttons in this article, I’ll make a small commission. Your price is unaffected.]

{ 79 comments… read them below or add one }

JOE HAGEDORN October 24, 2011 at 5:51 pm

I read the article and it is great. I will watch the video when I get a chance. I like having both the write-up and the video, it can answer a lot of questions. I have a wireless connection and my 1T external drive is built into my Apple wireless router. I do not fool with them unless I have a power outage, I switch on whatever buttons on the circuit breakers and nearby routers turn everything back on. Do I need to do something extra if I have a power outage? I have never checked to see if I have lost any data. I guess I better.


Steve October 24, 2011 at 8:47 pm

Hi Joe, glad you like the article. You point to an interesting challenge I have when I create each video and article. I think of them as a package, with the video placed into the article where I *think* it makes most sense. Although I do repeat some information in both the video and article, some things are only discussed in one or the other. Sometimes it’s easier to show something in video and sometimes text is best. Of course, I’m all ears if you have any specific or general suggestions for improvement.


Steve October 24, 2011 at 8:54 pm

Great question about dealing with a power outage. I think your backups should be fine as long as the power didn’t go out while Time Machine was performing a backup. Even then, the next time it attempts a backup it might be smart enough to see that the previous one didn’t complete. I know it recognizes that when you manually stop a backup.

The best solution is to get an uninterruptible power supply (UPS). You plug all your critical computer equipment into it and then it continues to power them during a power outage. (How long it does this depends on how much you want to spend on the UPS.) By “critical” I mean that you don’t have to bother plugging your printers and peripherals like that into it–just computer, router/drive.


Linda October 27, 2011 at 3:27 am

This site is proving to be invaluable, Steve. External hard drive has been ordered. Will return for installation instructions when it arrives.


Steve October 27, 2011 at 7:39 am

Great, Linda! I breathed a little sigh of relief as I read that.


Cindy October 28, 2011 at 12:15 pm

I’ve been meaning to write you to say how much I enjoy reading your newsletters and learning things about my iMac. It’s my first Apple product (I now have the original iPad also) and as a newcomer I really learn a lot from you. This particular newsletter (#18) couldn’t have been more spot-on for me. I just have had to replace my first external hard drive and I followed your instructions step-by-step. Couldn’t have been any better! I bought a 2TB Seagate Free Agent GoFlex for my desktop. It said the instructions would appear on my screen after I plugged in the USB and the power but they didn’t. So thanks to you I not only got it up and running very easily but also figured out what I may have done to disable my first external hard drive (not waiting for the Time Machine icon to disappear – didn’t realize it would do so).

I’ve passed along a subscriber’s link to your newsletters to a few other fairly new Mac users – hope they’ve subscribed. BTW, because I was wondering just what the GoFlex feature was and what it could do for me, I went to the Seagate website but was unable to find out. Do you happen to know? Thanks again for your continued help to us “Moms” with new Mac products.


Steve October 28, 2011 at 12:32 pm

Thanks, Cindy, for your sweet comment. I’m so happy to hear that you got your new external drive all set up. I just watched Seagate’s video about GoFlex. I can’t tell what, if any, unique features GoFlex might have. I suspect that they think it’s special because it’s upgradeable to faster interface speeds (USB 3.0, Firewire), or maybe that it plays well with their other GoFlex devices, like ones to connect to your TV? I can’t say that I saw anything Earth-shattering.


SUE October 28, 2011 at 12:38 pm

Steve – I’m confused. I have a RocStar time machine – isn’t that itself the back-up
for my hard drive.Must I also back up the RocStar?


Steve October 28, 2011 at 12:48 pm

Hi Sue. Yes, if you selected your RocStar drive as disk for Time Machine to use, then it should be a backup of your internal hard drive. But, if you want to be extra safe and follow the 3-2-1 Rule, then you’d also want a backup off-site. Maybe burning DVDs and storing them elsewhere, or using an online backup service like Carbonite.


Nev December 15, 2011 at 10:03 am

I agree.. I wasn’t backing up regularly and as soon as I did I lost something due to my own stupid fault. Back up drive saved my ass!!!!


Cindy January 30, 2012 at 6:18 pm

Hi Steve,
I always learn a little something, many times a big something. I have not been able to find the answer to this question on Apple support, does my Time Capsule back up iTunes TV shows I have purchased? Don’t laugh too hard at this question and assume that I did nothing custom with iTunes TV shows and movies. I can Enter Time Machine, click Music, click iTunes Music and find all my music, it appears to be all of my music. I can’t find anything that indicates the TV shows and movies I have purchased are backed up. My plan was to confirm purchased TV shows and movies were backed up so that I could delete them from iTunes allowing close to 100GB to free up on my hard drive. All of this so I can upgrade to Lion. Any ideas? Maybe purchased TV shows and movies can’t be backed up on my Time Capsule?


Steve January 30, 2012 at 7:20 pm

Hi Cindy,
I didn’t laugh at all. This is a good question. I have to admit that I’d never downloaded any TV shows in iTunes so I just tried one. Then, to discover where the show was stored on my hard drive, I selected it in iTunes (by single clicking on it) and then chose “Show in Finder” in the iTunes File menu. That opened up a Finder window that highlighted the TV show I’d highlighted. I was then able to learn that it was in my Music/iTunes/iTunes Music/TV Shows folder. Yes, iTunes is weird–it probably has your TV shows stored in “iTunes Music”.

So, first confirm that you can find your “TV Shows” folder on your hard drive. If you can, while viewing that folder in the Finder, start Time Machine. That should then show you the backup copies of the same folder. If that folder hasn’t been backed up, then open the Time Machine preferences, click on the Options button and check if the “TV Shows” folder has been added to the “Exclude these items from backups” list.

One big warning: If you delete TV shows from your hard drive, depending on the available space on your Time Capsule, the TV shows may not stay backed up there forever. If Time Machine needs more space for new backups, your backed up TV shows might be deleted since Time Machine will see that you don’t have them on your hard drive anymore and, thus, assume you don’t want them anymore.


Cindy January 30, 2012 at 8:06 pm

Thanks Steve! Didn’t know that I could find the TV shows on iTunes in Finder. That was very helpful. I have six seasons of a TV show mainly to watch on my iPhone. Finder groups each show not according to season but by show number. All second shows of each season are grouped together. Since the ultimate goal is to free up hard drive and after reading your Lion article it appears I have to clean up my Office for Mac and probably upgrade from Office 2008 to Office 2011. Falling dominoes, that what upgrading to Lion is like. Clean out iTunes, iPhoto, Pictures in Finder, upgrade Office and then finally upgrade to Lion.

Thanks again for your help!!!! I have sent a link to all my Mac friends to Mac Help for Moms.


Steve January 30, 2012 at 8:59 pm

Glad that helped, Cindy. And thanks for telling your friends!


Steve January 30, 2012 at 9:06 pm

Hey, I think Office 2008 should work with Lion. It should be a “Universal” application. Only “PowerPC” applications won’t work with Lion.


Cindy January 30, 2012 at 8:23 pm

Excluding items from backup
If I don’t specifically exclude Time Machine Backup it will back up the back up thereby using double the space? I’m imagining looking at a mirror in a mirror.


Steve January 30, 2012 at 9:08 pm

I think that used to be necessary but not anymore. I don’t Time Machine Backup listed in my exclusion list and I definitely don’t have a backup of my backup.


Steve January 31, 2012 at 8:52 pm

Oops, let me correct that. I wrote that when I was not connected to my external drive. Now that I have it plugged back in I see that “Time Machine Backup” is indeed listed in the exclusion list. But it is grayed out and I am unable to select it, so I assume that Time Machine automatically excludes the backups it creates and simply shows it in the exclusion list for completeness sake.


Mark February 8, 2012 at 4:21 pm

Hi Steve, I also have the experience of “time machine backups (221GB)” in the exclusion window and also grayed out. Were you able to confirm that this is as expected? I am using Snow Leopard OS. Is there a way I can check my time machine backups (original and ongoing increamental) are ok? There appear to be backups happening every hour. Thanks


Steve February 13, 2012 at 3:56 pm

Hi Mark, yes, I confirmed that Time Machine Backup should show up in the exclusion window.

I really need to make a video showing the other side of Time Machine–actually checking and possibly restoring from backups. Until I do, here’s the short version…either:

a) Choose “Enter Time Machine” from the Time Machine icon on the menu bar (if you have it displayed there), or

b) Launch the Time Machine application from your Applications folder.

In either case, you will enter a space-y (seriously) interface with a stack of windows showing which files were on your drive at various times in the past. In most cases this will be a stack of Finder windows, but if you are running iPhoto when you enter Time Machine, then it will be a stack of iPhoto windows, showing which photos/albums/etc. you had in the past. It works similarly with the Address Book and Mail applications too. Play around with it to confirm that you have backups of what you expect.

jac mills March 14, 2012 at 4:31 pm


Just looked at Time Machine backup. Did not realize you have to have an external drive to do so. That is how stupid I am. Any recommendations for buying? Thanks.



Steve March 14, 2012 at 4:49 pm

Hi Jac!

Well, you don’t absolutely have to have an external drive. If you have a desktop Mac with two internal drives I guess you could back up from one to the other. But an external drive is handy because in case of emergency you can just grab it and run!

All my recent experience has been with Western Digital drives. I’ve got a couple portable 250GB ones that are now too small for my stuff but I sometimes plug in to make a second backup of important files. My son has a 1TB USB backup drive and I just switched to a 3TB network drive. All Western Digitals.

The USB drives will be faster than a network drive so I recommend a USB drive unless you absolutely need a network drive for the flexibility of backing up from anywhere in the house or want to also use it to share music or video amongst multiple computers.

I put an Amazon widget up in the article that should always display the current prices of 1TB and 2TB desktop models and a 750GB portable model (which could fit in a pocket). I’m shocked to see that the prices are actually a bit higher than when I wrote the article in October–maybe they had holiday pricing then. Anyway, if you don’t mind the larger desktop model, I see $122.99 for the 2TB model right now. Is your peace of mind worth that? :-)

You just have to click on one of those pictures in the article to be whisked off to Amazon. I’ll make a few bucks if you use those links. I can tell that some people were inspired to buy backup drives because I’ve already made enough commissions for a few coffees.


Charles April 11, 2012 at 3:54 pm

Great site. Thanks. One question though. I’ve done everything you suggested. A 1T drive to back up a 250GB HD on my mac mini. What I’ve noticed though is that as the drive has filled up, it spends more time chattering away. Sometimes for hours on end. Very annoying. Is there anything that I’m doing that could be causing that or is that the nature of Time Machine? Thanks


Steve April 23, 2012 at 2:25 pm

Hmmm, Charles, how full has your backup drive gotten? I’ve been experiencing a similar problem (backups taking much longer than they should) but I think that’s related to me switching to a network backup drive. I’m still trying to solve my problem.

One thing you could try is installing the Time Machine Buddy widget on your Dashboard.

It can give you some insight into what Time Machine is doing during a backup and also let you log at the logs from previous backups. You could then copy and paste the log from one of your backups into an email to me, and I could try to figure out what’s causing your slow backups.


Brittany April 23, 2012 at 2:09 pm

Hi Steve, I backed up my macbook pro on my external hard drive using time machine but now my computer won’t back itself up unless the external is plugged in…I am guessing I have somehow told it not to automatically backup on its internal hard drive but I’m not sure how to change it back since I’m not given that option in the time machine box. Do know how I can fix this??

Thank you!!



Steve April 23, 2012 at 2:28 pm

Hi Brittany, I’m a bit confused. Before backing up to your external hard drive, did you somehow backup to your internal hard drive? Do you have two internal hard drives? If you only have one it wouldn’t make sense to backup to itself, and I’m not even sure Time Machine would let you do that.


Brittany April 23, 2012 at 2:35 pm

I’m pretty sure I only have one internal hard drive because I just bought the standard macbook a few months ago and I think they only come with one. I’ve compiled a bunch of stuff on my computer since then so I wanted to back it up on the external. Before this I had a PC and so that computer was backed up on this same external hard drive. When I plugged it in to the mac it didn’t recognize it because I guess it was formatted wrong. So, I dumped everything from the external onto my mac and wiped out the external. Then I backed up everything now on the mac back onto the external. Since then, my mac only backs itself up when the external is plugged in because I think I somehow shut off the internal hard drive but I don’t know how to turn it back on. Does that make any sense?


Steve April 23, 2012 at 2:45 pm

Copying PC backup content onto your Mac, wiping the external, then backing up the Mac to the external all sounds great. Good job! Since the external is your backup destination, it makes complete sense that Time Machine would only backup to it when it was attached. That’s how Time Machine works–if the external isn’t attached it just silently waits until it is connected again.

But, unless I’m missing something, I doubt your Mac was doing any backups before you set up Time Machine to backup to the external drive. On a new Mac, Time Machine isn’t set up to do anything until you plug in an external drive and then do the minor setup of Time Machine that it sounds like you’ve already done.

That’s why I strongly urge Mac users to backup to an external drive, because before they do they aren’t backing up at all!

Make sense?


Brittany April 23, 2012 at 2:49 pm

ohhh ok, I thought I did something wrong because when the external isn’t plugged in that time machine icon in my tool bar has an ! symbol over it saying it wants to back up but can’t. So, I don’t have to plug in the external each time this symbol pops up? How often should I be backing everything up? Because right now it wants to back up on the external every hour which seems excessive…


Steve April 23, 2012 at 3:02 pm

The general rule is “back up frequently enough so you won’t mind losing *everything* since your last backup”. If you’re at home (or work, or wherever you keep this MacBook the most), why not have the external drive attached all the time (except maybe when it’s in your lap while watching TV)?

Don’t worry about the hourly backups. Time Machine is only backing up the files that have changed since the last backup. Also realize that if you are spending a lot of time working on a file (for instance, a document), Time Machine will store hourly copies for the past 24 hours, daily copies for the past month, and weekly copies older than that (unless your external drive gets full, in which case the oldest ones get deleted). That lets you retrieve an earlier copy if decide you don’t like some changes you made to the document.


Brittany April 23, 2012 at 3:37 pm

oh okay that’s good to know. thank you for your help!!


diane May 17, 2012 at 8:58 am

a question… i bought a WD passport 500GB thinking to use it as external storage to free up space on my Mac. it is running now as the time machine backup destination. Can I (or do I need to) copy/transfer big files (iphotos etc) separately to be able to store them externally to free up my internal hard disk? when i checked a back up of the Iphoto library it said it was not intended as archival storage. Is this passport now exclusively dedicated as a back up device and i need another for external storage?


Steve May 24, 2012 at 11:21 am

Hi Diane. Just catching up after being away for a week. I just answered a similar question by Howie, so please read my replies to him. In short, yes, you really should get another external drive if you want to free up space on your internal hard disk. Even though you could, in theory, have two copies of a file on your single external drive (one managed by Time Machine and another that you manually placed there), that really doesn’t count as a backup, since the failure of that single drive would wipe out both copies.

You might want to also read the article I linked to above. Look for “3-2-1″ in my October 28, 2011 reply.


howie May 23, 2012 at 12:30 pm

thanks for that. i’ve just bought my first external hard drive and am in the process of doing the first back up.

my question is… once i’ve backed up successfully, can i delete some of the large video files from my computer?

I also want to run my itunes library from the external rather than clog up the hard drive on my desktop. what’s the best way of doing that?



Steve May 24, 2012 at 11:09 am

Hi Howie. No, even though you’ve backed up files (like those large video files) to Time Machine, you shouldn’t delete them from your main drive for TWO reasons.

(1) The purpose of backing up is to have an *additional* copy of your files. Your backup drive is just as likely to fail as your main drive–the point is that by having two (or more) copies of everything, then either can fail and you won’t lose anything.

(2) Time Machine will keep multiple versions of files you change so that means that over time your Time Machine backup will take up more space than your main drive. If the backup drive fills up, then Time Machine will delete the oldest versions of files. It will always keep at least one copy of each file that’s on your main drive AS LONG AS it’s still on your main drive. If you delete those large video files, then some time in the future Time Machine might also delete them from the backup in order to make space for other files.

So, if you want those video files backed up AND off your main drive, I suggest getting another external drive, clicking the Options button in Time Machine Preferences and making sure the new external drive is NOT excluded from backups, and then moving your large video files from your main drive to the new (second) external drive. Then they’ll be off your main drive but still backed up to your Time Machine backup.


Steve May 24, 2012 at 11:13 am

As far as storing your iTunes library on an external drive, I suggest you put them on the same new external drive I just suggested for your large video files.

Time Machine backups aren’t really meant to be accessed by other applications, so you couldn’t have iTunes read the copy of your library that Time Machine backed up.


Jennifer May 23, 2012 at 4:25 pm

Hi Steve,

I just found your site and love it! Quick question, I am upgrading my macbook pro and imac to Lion. Prior to the upgrade, I am planning on backing up my data via time machine to an external harddrive. My plan is to use 1 external hard drive for both computers and then update/maintain the time machine back ups on a weekly basis. Should I have any concern for re access to data backed up when still using snow leopard after upgrading to Lion? Will the external drive automatically set up 2 different time machines back ups for the 2 computers? Thanks for your help.


Steve May 24, 2012 at 11:31 am

Hi Jennifer! Let me answer the easy question first. Yes, you can definitely back up two computers using Time Machine to a single external drive. But don’t give the drive credit for this, it’s Time Machine that has the smarts to associate each backup with the computer it came from.

I’m a little confused about your question about still using Snow Leopard after upgrading to Lion. Do you mean Snow Leopard on one of the computers and Lion on the other? If so, then no problem. Each computer’s backup is independent of the other and they can be from different versions of the operating system.

If, instead, you meant accessing your backups made under Snow Leopard once you upgrade to Lion, then that shouldn’t be a problem either. Let me know if you meant something else.


Tim May 24, 2012 at 10:25 am

Using 10.7.4 and time machine backsup great. Problem is when I try to open time machine, instead of going to past backups, it doesn’t do anything. Why? Used to work….


Steve May 24, 2012 at 11:37 am

Hmm, doesn’t do anything? Do you even get the screen filled with stars?

Feel free to use the “Got a Questions?” link on the top or bottom of this page and then we can start an email conversation where you could send me a screenshot of what you’re seeing (if anything).


Hugo Cox June 1, 2012 at 1:06 pm

What I find strange is that each time Time Machine backs up my computer it takes about 45m. I do a back-up weekly. This week there can only be a handfull of word files I created and a few pdfs that I saved. Am I missing something? (Friends have suggested the drop box may be a better solution for me) Many thanks for your very helpful piece, by the way. regards Hugo


Steve June 1, 2012 at 1:20 pm

Hi Hugo! Yeah, Time Machine often takes that long or longer for me too. I think I have something messed up that causes it to think that more files have changed than really have. I’m still investigating and will report back if I learn anything.

But doing less frequent backups (like weekly) instead of the default hourly backups actually causes more work for Time Machine because then it has more expired backups to delete. (It will always keep at least one copy of each file, but since it keeps hourly copies for the past 24 hours, daily copies for the past month, and weekly copies older than that, sometimes it needs to purge some copies.)

I use DropBox too but I don’t consider it an alternative to Time Machine. I use it in addition! So all my stuff is backed up by Time Machine and then I also store my most important stuff (and especially the files I might want to access from my iPhone, other computers, etc.) in my DropBox folder. Once set up I don’t have to actively do either, since Time Machine naturally backs up my DropBox folder, which DropBox is also magically copying up into the “cloud” (their computers).


Gaurav June 5, 2012 at 11:22 am

Hi Steve,

Please pardon me if i cannot frame my question correctly.

I purchased WD Passport Studio 1Tb (FireWire and USB 2.0) for my Mac Pro 15 Inch. Yesterday, I set up the Time Machine and started my 1st back up. During 1st backup total estimated data for back up shown was 80 GB but just to test the back up process I excluded most of things which caused Time Machine and Back Up freeze.

After that I did force quit and re-attached my WD Drive to Mac and then it was doing lot of grinding and squeaking sound and won’t appear on Mac. After 3 or 4 trail of taking cables in and out, it appeared on Mac.

Once appeared I restarted back up process and it only showed 33 GB to back up which was less than early 80 GB of data. Although this back up ran smooth without any noise. Also, in first go it was showing external hard drive as exclusion but now there is nothing in exclusion list.

Please advise if there is something wrong with Drive (I purchased from B&H Photo) and should i return it or should i give few more tries of back up. Also, how now i can back all data. You help will be greatly appreciated on this issue.


Steve June 5, 2012 at 2:18 pm

Hi Gaurav,

I would give it a few more tries since you said the backup ultimately ran smoothly. I fear some of your early failed attempts were due to using Force Quit and not properly ejecting the drive. It’s very important to always eject the drive before unplugging it.

As far as backing up all your data, just remove all those things you added to the exclusion list.

Things like the external hard drive will only show in the exclusion list when they are plugged into the computer. Was it unplugged (or not recognized) the time you didn’t see it in the exclusion list?


Gaurav June 5, 2012 at 5:31 pm

Hi Steve,
There was nothing showing up on my exclusion list so I erased my Hard Disk. Now, my HD shows full 1TB available and time machine back has started and running fine now.
Only concern I have is that now only 27 GB of data was recognized to be backed when last run it backed up around 33 GB. Why it is continuously reducing the Data to be backed up. Please advise. Thanks again for your important time.


Gaurav June 5, 2012 at 7:57 pm

Hi Steve,

Just to tell again I have tried the back up 3 times after complete erase and every time it is backing up only 33 gb of data even though my disk is 85gb full. Then why it is not backing up all files. Please advise


Gaurav June 10, 2012 at 7:38 am

Hi Steve,
I was able to resolve the problem by resetting the time machine. Now it backed up whole 80 gb of data. And thanks for all your help.

Mel June 11, 2012 at 12:18 pm

Having followed advice re erasing/partitioning etc (as per Apple Support Community) backup still stopping after exactly 7.06GB (as before). Imac OSX 10.6.8. External drive is Buffalo HD-PC500U2/BK-EU which works fine without Time Machine provided I just back up images etc and not the whole Macintosh HD.


Steve June 11, 2012 at 12:29 pm

Hi Mel, does it completely STOP after 7.06GB and act like it thinks it completed the task? Or does the counter just stop changing at 7.06GB? Often the counter can look stuck for quite awhile and then catch up in bursts. I suspect it’s because it only updates the counter after each file, and not in the middle of backing up really large files.


BusMgr June 16, 2012 at 7:29 pm

Hi Steve,

Maybe you’ve answered this already and I just didn’t see it – it seems like Time Machine isn’t really the ultimate backup solution b/c it sits in the same physical space as your computer so if there was a fire or theft everything would be lost. I have heard that you shouldn’t really juggle multiple Time Machine disks because they build on one another. What do you recommend for the best off-site security backup system? I know some people say to store stuff online. We have a lot of photo and video files so I don’t know what the costs would be on something like that. Any suggestions?


Steve July 1, 2012 at 12:14 am

Hi, you are correct that Time Machine isn’t really meant to be used to maintain two sets of backups, although it is able to. But, since Time Machine keeps multiple versions of files that are modified, each backup would have a different disjointed history for each file. So, doable, but as you say, definitely not “ultimate”.

An application that many people use for making a simple backup is Carbon Copy Cloner (CCC). An excellent off-site backup process would be to have two external drives on which you put full backups created by CCC. Always keep one off-site. After you create a new backup on the on-site drive, take it off-site and return home with the older backup. Perform this daily, weekly, monthly, or whatever schedule makes sense with how often you add new photos, videos, etc.

There are also online backup solutions like Carbonite that would satisfy your desire for an off-site backup. Depending on your Internet connection and how much you back up, it might take quite awhile to get everything copied into Carbonite’s system, but after that it should be pretty invisible and no effort.


anders w June 29, 2012 at 3:47 am

I have time machine backing up to an external harddisc. I have put some encrypted sensitive files ( passwords etc ) on an USB. When I decrypt them on the computer will the decrypted files be stored on my external harddisc?


Steve June 29, 2012 at 11:27 am

Excellent question Anders. Everything on your primary drive will be backed up to your external drive UNLESS you explicitly exclude particular files or folders. To do that, click the “Options…” button in Time Machine Preferences and then click the + button to add the items you want to exclude from your backups. To make this simple I’d suggest creating (or choosing) a folder where you do all your decryption of those sensitive files, and then exclude that folder in Time Machine Preferences.


Jacky June 29, 2012 at 4:37 am

I just bought WD My Book for my Mac 2 TB/To external drive and this could be a really stupid question but do i have to leave the power souce plugged into the power point while im backing up or can i just have it connected to my Mac Book Pro Its just that im at work and and have to go home soon but im not sure if i can move it i do not want to disrupt the download process as i have just had an external hard drive lose all its data on me today and do not need to lose anything else


Steve June 29, 2012 at 11:34 am

If your external drive has a power cord (some just get all their power through USB) then you have to leave it connected to power. But, you can stop a Time Machine backup and it will pick up where it left off the next time it runs. But be patient and let Time Machine completely stop (it may take a minute or two) after you tell it to stop. Also, (and this is true ALL the time) be sure to use the eject function on all USB drives before you physically unplug it from the computer.

Your other instincts are correct. You shouldn’t move any hard drive while its spinning. You’ll probably get away with it many times if you’re careful but ultimately it will reduce your drive’s lifespan and increase the odds of getting an error.


kanne July 18, 2012 at 9:56 am

Hi Steve,

I have a WD My Passport Studio that I would like to use to back up ONLY iPhoto pictures and videos from iMovie on my MacBook Pro. Is this a reasonable use of Passport? I want to be able to remove these pictures/movies off of my hard drive to free up space. I do not want anything else backed up from hard drive onto this particular external drive.



Steve July 24, 2012 at 1:21 am

Hi Kanne, this is a perfectly fine use of your Passport BUT you should NOT consider this a backup if you are going to remove the images and movies from your main hard drive. If you only have one copy of those files, they are NOT backed up.


Shaunt July 21, 2012 at 12:56 am

Howdy. Quite frustrated. I’ll give you the facts first:

– I started running low on my Macbook Pro hard disk.
– I do have a time machine as a back up device.
– I also have Icloud, Idisk and Itunes Match to back up music/apps.
– I purchased a WD 3TB external hard drive.
– I Moved my music to my WD 3TB external hard drive.
– I Deleted music from my Macbook Pro hard disk drive.
– After a month or two my WD 3TB external hard drive stops being recognized by the finder. Some malfunction.
– I have the WD 3TB external hard drive replaced, though of course, it’s empty.
– I must now retrieve my music and get it all back onto this new WD 3TB external hard drive.
– My music is on Itunes match and yet I can’t “GET IT” onto my computer. I can access my music on my work computer….but for some reason, not on my original home computer. I don’t see a button or place to accomplish this transfer.
– In desperation, I decided to go into my Time Machine, find the music folder from a few months ago and RESTORE to my external hard drive.
– However, there is not enough space on my MacBook Pro to hold the music.

HOW do I tell my time machine to send the music files to my 3TB WD external hard drive instead of my Macbook’s hard drive?

Really appreciate any help you can offer!



Steve July 24, 2012 at 1:18 am

I don’t yet have a solution for you, but I do need to clear up a subtle (but common) misunderstanding you may have about how Time Machine works.

Once you delete something from your main drive, Time Machine may not keep backup copies of these forever. So, when you moved your music to the WD 3TB drive and removed the music from the main drive, that gave Time Machine the message that you might not want those files anymore. Time Machine didn’t immediately delete the music backups, and wouldn’t ever delete them if the Time Machine drive had lots of free space, but if it starts running out of space, it could start purging those music backups.

If you use Time Machine’s Restore button, it only restores files back into the folder in which they originated. But, I think you might be able to right-click (or Control-click) on files or folders in the Finder in Time Machine and choose something like “Restore to …”, which will then give you the opportunity to select your new WD 3TB drive as the restore location. I’m away from my Time Machine drive right now so I can’t check this out firsthand.


Dana July 30, 2012 at 11:50 am

Steve….I just purchased a WF 500 GB My Passport to use with Time Machine, but noticed that it seems to be running after the backup as finished….is that normal?? Also, I turned off the auto backup because I thought backing up hourly was a little excessive and would wear out my external hard drive faster. But after reading your forum it sounds like I should just let it do it’s thing, right?


Steve July 30, 2012 at 11:27 pm

Hi Dana, external drives don’t shut down just because Time Machine is done backing up. After awhile they may go into a sleep or energy saver mode, depending on the model and configuration.

Yes, I agree with your second guessing. Even hourly backups won’t create as much activity on your external drive than your internal drive normally gets, so I wouldn’t worry.


Dana July 31, 2012 at 5:37 am

Thanks so much for your time!!! I appreciate your input greatly! I have one more question though….I bought the external hard drive the same size as my iMac hard drive but in reading some of the discussions here, should I have bought one 2-3 times larger??


Steve July 31, 2012 at 4:19 pm

Maybe. Here are a couple things to consider.

(1) You don’t need to base the size of your external drive on the *capacity* of your internal drive, just how much of the space you expect to use. So if you have a 300GB internal drive but only use 100GB of it, a 300GB external drive should be more than adequate. I was biased in my 2-3 times statement above because my internal drives always seem to fill up!!!

(2) The reasons to have a backup 2-3 times larger than the stuff you’re backing up is so (a) Time Machine can maintain numerous copies of the daily, weekly, monthly versions of frequently modified files and (b) Time Machine has some working space in case a bunch of files have changed or been added since the last backup.

As long as your backup drive is a little bigger than what you have to back up, you’ll have at least one backup copy of every file.


Dana July 31, 2012 at 6:51 pm

Perfect….thanks a lot!!!!


Andrew November 6, 2012 at 10:26 pm

hi, very informative post! i have one question, i have 2 external drives, one for tv/music and one for everything else.. i have 900gb free on one of them, and need to back up my computer to get the internal HD replaced.. does the HD i will be using for Time Machine have to be reformatted, or can i leave my current data on it? (i have previously used this same HD for a time machine backup, so the format is definitely correct). the backup will only take up about 400GB. thanks for your time :)


Steve November 6, 2012 at 10:43 pm

Hi Andrew. Yes, you definitely should be able to use that drive as is. Just a few comments:

  • Time Machine needs working space while performing a backup. The working space is proportional to the amount being backed up. It’s possible that a backup of 400GB of files may not start unless you have 600GB of space. It ultimately will only use 400GB but it thinks it needs 200GB of working space. I could be overestimating, but just be aware.
  • If this drive has an old Time Machine backup from the same computer, then Time Machine will likely try to update that instead of just doing a fresh backup. Carefully watch the Time Machine messages as the backup commences. A handy tool that lets you watch the Time Machine log in real-time is the Time Machine Buddy Dashboard widget. If you need help with the Dashboard, check out my What is the Dashboard and what are its widgets? article.

So, are you taking this opportunity to replace your internal drive with an SSD drive? I don’t have one yet but everyone I know who does just loves it.


Nicole Wong January 14, 2013 at 12:13 am

Hi Steve, I’ve just bought myself a 1TB Seagate FreeAgent GOFLex Ultra-portable drive and I didn’t know how to set it up initially since there isn’t any proper instructions to follow on how to set up the External HD. So, I found out a video on YouTube and followed the steps that were shown and set my HD into Time Machine backup where it backups all the time and it is in Mac OS Extended (Journaled). But my initial motive to buy the HD is for the purpose of using it as an external hard disc for the use of both on PC and Mac, and to back up once in awhile from my Mac and since I’ve fully use up three quarters of my Mac’s memory I want my HD to be just ordinary hard disc. Any remedy to my situation? Please help. Urgent.


Steve January 14, 2013 at 1:18 pm

Hi Nicole, you offer quite a challenge. As it sounds like you may have discovered, Time Machine requires the external drive to be formatted as “Mac OS Extended (Journaled)”, which Microsoft Windows doesn’t know how to read. Your Mac knows how to format the drive as “MS-DOS (FAT)” so Windows can read it, but Time Machine won’t work with that format. I can think of two possible solutions:

  1. Using Disk Utility (in Applications / Utitilies) re-partition your external drive into two partitions. Make the first partition “MS-DOS (FAT)” (to be used by the PC, and Mac too if you want) and the second one “Mac OS Extended (Journaled)” to be used by Time Machine. This will mean that your current Time Machine backup will be erased and you’ll have to start over with Time Machine.
  2. Or, on your PC, install an HFS+ file system driver so that Windows can read your external drive as it is now. (HFS+ is just another name for Mac OS Extended.) I haven’t tried any of these, but HFS+ for Windows has a 10 day trial so you could give it a try before you buy. If that works, just make sure you don’t mess with the Time Machine Backup folder on your external drive. It’s put perfectly fine to put non-Time Machine files outside of that folder.

If you try the HFS+ for Windows, please report back how it works for you.


Nicole Wong January 14, 2013 at 10:41 pm

Thanks for the immediate response. But may I ask how can I make two partition for my HD?


Steve January 17, 2013 at 10:53 pm

Hi Nicole, it’s a little complicated and can result in you losing all the data on that disk, so let me point you directly to Apple’s help. Launch the Disk Utility application from the Utilities folder within your Applications folder. Once it’s running, go to its Help menu and choose Disk Utility Help. Then look for a section called “Changing a disk’s partitions” and read all those instructions.


Lexi February 26, 2013 at 9:29 pm

Hi Steve! Great post. I was recently gifted a MacBook Pro along with an external drive to store all my pictures and movies on since the new Pros have such limited space. On a recent visit to an Apple store I was told I would need to buy a second external drive to use exclusively for Time Machine backups, since the other external is simply being used as additional storage. Do you know if that is accurate-must I buy two seperate hard drives- one for storage and one for backup? TIA!


Steve February 26, 2013 at 9:47 pm

Hi Lexi. Last I checked it wasn’t an absolute requirement to have two separate drives, but it’s highly recommended for numerous reasons. For one, if you had Time Machine backup to the same drive you use to store pictures and movies, then those pictures and movies (which I assume are valuable to you) won’t be backed up on another drive. Remember, ultimately all hard drives fail, so everything of value should be on at least two drives.

So, if that convinces you to get a second external drive for Time Machine, be sure to check your Time Machine Options to make sure your picture/video drive isn’t excluded from Time Machine backups.


Lexi February 26, 2013 at 10:00 pm

Thanks Steve! That makes complete sense, I can now better explain to my husband why I need a second drive :)


Dana March 23, 2013 at 8:49 pm

Hi-just bought a WD 1TB to back up my MacBook Pro. I’m scared to go past the first pop up asking if I want to use “my passport for Mac” to back up with machine? I can’t decide if I need to select use or don’t use. I’m rather Mac illiterate. Any advice would be appreciated. By the way, I couldn’t get your video to play.


Steve March 28, 2013 at 10:04 pm

Hi Dana, I think we should figure out why you can’t play the video on this page, because the video should answer your question (hint: the answer is “Use” if you want to use that drive for Time Machine backups). Are you able to view any videos on the site?


Nancy April 23, 2013 at 8:51 pm

I looked so long to get a teacher who could be basic and thorough as you were. Your patient approach was like a breath of fresh air! Now I feel confident with this task.
Thanks so much,


Gaz June 21, 2014 at 9:40 pm

Thanx Steve
Very lucid explanation. I am now doing the backup deed, and feeling very clever. Many thanks for sharing.


Gerry Maguire February 1, 2015 at 12:25 pm

This is a great feed, thank you so much.
My wife and I have separate log ins on our MacBook Pro. I have just bought the WD back up. Do I need to run in both log ins? I hope this isn’t covered already.
Thanks for all your useful work in this, it’s really very helpful to a novel like me.


Steve February 1, 2015 at 10:44 pm

Hi Gerry, no I didn’t cover that. It’s a great question. You do NOT need to set up Time Machine individually for each login. Time Machine backs up all users’ files unless you explicitly configure it to exclude folders associated with a user. If you didn’t do that then you’re fine.


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